1. Field of the Invention
The present invention is the method of preparing ethers with unsaturation in one or both of the groups attached to the ether oxygen atom, by the catalyzed reaction of an allylic halide with an alcohol.
Ethers with such unsaturation are useful as, e.g., comonomers in the polymerization of epichlorohydrin and related epoxy monomers, in the preparation of drying oils, and specialty solvents.
2. Description of the Prior Art
Ethers with unsaturation in one or both of the groups attached to oxygen are known in the art. Heretofore, methods for making the di-unsaturated ethers have been commercially unattractive, e.g., by the removal of alcohol from an acetal.
U.S. Pat. No. 1,941,108 discloses a process for making mono-olefinic ethers by reacting a vinyl halide, an alkylidene halide or an alkylene halide with an alcoholate of the aliphatic, cycloaliphatic, aliphatic-aromatic or aromatic series alcohol in the presence of an organic diluent, solvent or suspending agent. A similar process is shown by U.S. Pat. No. 2,042,219 wherein mono- or di-unsaturated ethers are produced by reacting a suitable unsaturated hydrocarbon halide with an alcohol under aqueous alkaline conditions, the examples of the latter showing the use of aqueous sodium or potassium hydroxides and solid calcium oxide in water [Ca(OH).sub.2 ?].
Similarly, U.S. Pat. No. 2,382,031 describes a method of making the diether of isoprene alcohol starting with an isoprene-containing gas oil stock by first reacting the isoprene with hydrogen chloride to form isoprene monohydrochloride, hydrolyzing the latter with caustic alkali to form isoprene alcohol, and then converting the latter compound to the diisoprene ether by several methods including (a) reacting the alkali metal alcoholate of isoprene alcohol with isoprene monohydrochloride, (b) dehydration of isoprene alcohol with H.sub.2 SO.sub.4, and (c) by reaction of isoprene alcohol with isoprene monohydrochloride in the presence of alkali.
It is also known in the art to make mono-unsaturated ethers by reaction of a diene with a saturated alcohol. However, when attempting to produce the unsaturated ethers of the present invention by reacting dienes with unsaturated alcohols, economically unattractive amounts of the symmetrical ether formed by the reaction of two molecules of the unsaturated alcohol are produced. Attempts to suppress the undesired reaction without deleterious effect on the alcohol-diene addition have been unsuccessful.
It is also known, as in U.S. Pat. No. 3,271,461, to react a diene with a saturated alcohol in the presence of (1) a cuprous halide catalyst and (2) an acid co-catalyst. Such a process is a very slow process requiring reaction times of up to 100 hours as shown in the patent. While such patent indicates that the alcohol ingredient can be unsaturated (but shows no example thereof), it has been found that the method actually is inoperative with unsaturated alcohols. It has been found that, unlike saturated alcohols, the unsaturated alcohol reacts quite readily with any hydrohalogen acid liberated forming water which, in turn, hydrolyzes the copper halide catalyst diactivating same and/or causing separation of an aqueous phase which will contain all the copper catalyst in inactive form and the organic phase contains small amounts of a diether of the unsaturated alcohol. When the process of the patent is carried out with an unsaturated alcohol at the higher temperatures recited therein, the dehydration of the unsaturated alcohol is increased forming sufficient water to cause phase separation. The examples below show the effects.
Thus, the prior art methods for making ethers containing at least one hydrocarbon group containing a carbon-to-carbon double bond have operated under either strongly basic conditions employing alcohol-soluble alkalines or strongly acidic conditions. Contrary to this art, the great value of copper halide catalysts when employing unsaturated alcohols has not been realized.